Miscible blends of imide containing polymers with poly(aryl sulfones)

ABSTRACT

This application relates to miscible blends of biphenyl containing poly(aryl sulfones) and isopropylidene based polyimides. These blends are suitable for printed wiring board substrates, flexible printed circuit boards, electrical connectors and fabricated articles requiring heat and chemical resistance. A method for extruding these articles is taught.

This is a division of application Ser. No. 291,967, filed Dec. 30, 1988now U.S. Pat. No. 5,037,902.

FIELD OF THE INVENTION

Applicants teach about unique combinations of select imide containingpolymers that contain an isopropylidene group which are miscible withbiphenyl containing polysulfones, and processes for using suchcombinations. These blends are suitable for printed wiring boardsubstrates, flexible printed circuit boards, electrical connectors andother fabricated articles requiring high heat and chemical resistance,and good dimensional and hydrolytic stability. They are particularlysuitable for use as matrix resins in thermoplastic continuous fibercomposites.

BACKGROUND OF THE INVENTION

Applicants have directed their attention to making miscible blends ofpolymers having utility as composite matrices for advanced compositeaerospace uses and for use as general purpose injection molding resins.Rather than directing attention to miscible thermoplastic blends, theprior art has been directed to blends of thermoplastics without regardto whether or not they are miscible.

U.S. Pat. No. 4,293,670 to Robeson et al describes molding compositionsof blends of poly(aryl ether) resin and a polyetherimide resin. Thepoly(aryl ether) resin is taught to be a linear, thermoplasticpolyarylene polyether wherein the arylene units are interspersed withether, sulfone or ketone linkages. Particular formulae ofpolyetherimides are taught in the reference. A molding compositioncomprising blends of these materials is claimed and exemplified in thereference.

U.S. Pat. No. 4,713,426 describes blends of a biphenyl containingpoly(aryl ether sulfone) and a poly(aryl ether ketone). The referenceteaches that these blends have limited miscibility and excellentmechanical compatibility. According to the reference, these blendspossess, in an article molded therefrom, a good balance of propertiesincluding higher modulus, impact resistance, solvent resistance andresistance to environmental stress cracking. As taught, the poly(arylether ketones) are used because they offer an exceptional balance ofproperties, namely, high melting point, excellent thermal stability,excellent hydrolytic stability, high stiffness and strength, goodtoughness, and excellent solvent and environmental stress ruptureresistance. The reference specifically teaches that the results indicatethat a low level of miscibility is observed in these blends as the glasstransition temperature of the poly(aryl ether sulfone) is slightlydecreased. However, the blend contains separate glass transitiontemperatures for each of the components of the blends.

U.S. Pat. No. 4,684,674 to Brooks teaches another blend. Specifically,the reference teaches polyamide-imide-phthalamide copolymers andpolyamide-imide copolymers containing aromatic sulfone polymers.However, the blends are two-phase and exemplified by two glasstransition temperatures, one for each of the components of the blend.The reference teaches that a completely miscible system exhibits asingle glass transition temperature (T_(g)) while immiscible blends havetwo T_(g) 's, each at the temperature of one of the components. Thereference specifically teaches that the polyamide-imide/polyethersulfoneblends taught in the reference show no evidence of a system which ismiscible.

World Patent Application No. WO 8604-079A describes blends ofphenylindane containing polyimides with polyetherimides, polysulfones,polyarylether ketones, polycarbonates, polyarylates or polyphenyleneoxides. The compositions are claimed to be useful as adhesives, coatingsor matrix resins in carbon fiber reinforced composites.

In the field of miscibility or compatibility of polymer blends, theprior art has found predictability to be unattainable, even thoughconsiderable work on the matter has been done. According to theauthorities:

(A) "It is well known that compatible polymer blends are rare". Wang andCooper, Journal of Polymer Science, Polymer Physics Edition, Vol. 21, p.11 (1983).

(B) "Miscibility in polymer-polymer blends is a subject of widespreadtheoretical as well as practical interest currently. In the past decadeor so, the number of blend systems that are known to be miscible hasincreased considerably. Moreover, a number of systems have been foundthat exhibit upper and lower critical solution temperatures, i.e.,complete miscibility only in limited temperature ranges. Modernthermodynamic theories have had limited success to date in predictingmiscibility behavior in detail. These limitations have spawned a degreeof pessimism regarding the likelihood that any practical theory can bedeveloped that can accommodate the real complexities that nature hasbestowed on polymer-polymer interactions." Kambour, Bendler, Bopp,Macromolecules, 16, 753 (1983).

(C) "The vast majority of polymer pairs form two-phase blends aftermixing as can be surmised from the small entropy of mixing for verylarge molecules. These blends are generally characterized by opacity,distinct thermal transitions, and poor mechanical properties. However,special precautions in the preparation of two-phase blends can yieldcomposites with superior mechanical properties. These materials play amajor role in the polymer industry, in several instances commanding alarger market than either of the pure components." Olabisi, Robeson, andShaw, Polymer-Polymer Miscibility, Academic Press, New York, N.Y., p. 7(1979).

(D) "It is well known that, regarding the mixing of thermoplasticpolymers, incompatibility is the rule and miscibility and even partialmiscibility is the exception. Since most thermoplastic polymers areimmiscible in other thermoplastic polymers, the discovery of ahomogeneous mixture or partially miscible mixture of two or morethermoplastic polymers, is, indeed, inherently unpredictable with anydegree of certainty; for example, see P. J. Flory, Principles of PolymerChemistry, Cornell University Press, 1953, Chapter 13, p. 555." Younes,U.S. Pat. No. 4,371,672.

(E) "The study of polymer blends has assumed an ever increasingimportance in recent years and the resulting research effort has led tothe discovery of a number of miscible polymer combinations. Completemiscibility is an unusual property in binary polymer mixtures whichnormally tend to form phase-separated systems. Much of the work has beenof a qualitative nature, however, and variables such as molecular weightand conditions of blend preparation have often been overlooked. Thecriteria for establishing miscibility are also varied and may not alwaysall be applicable to particular systems." Saeki, Cowie and McEwen,Polymer, vol. 25, p. 60 (January 1983).

Thus, miscible or compatible polymer blends are not common. The criteriafor determining whether or not two polymers are miscible are now wellestablished. According to Olabisi, et al., Polymer-Polymer Miscibility,supra p. 120:

"The most commonly used method for establishing miscibility inpolymer-polymer blends or partial phase mixing in such blends is throughdetermination of the glass transition (or transitions) in the blendversus those of the unblended constituents. A miscible polymer blendwill exhibit a single glass transition between the Tg's of thecomponents with a sharpness of the transition similar to that of thecomponents. In cases of borderline miscibility, broadening of thetransition will occur. With cases of limited miscibility, two separatetransitions between those of the constituents may result, depicting acomponent 1-rich phase and a component 2-rich phase. In cases wherestrong specific interactions occur, the Tg may go through a maximum as afunction of the concentration. The basic limitation of the utility ofglass transition determinations in ascertaining polymer-polymermiscibility exists with blends composed of components which have equalor similar (20° C. difference) Tg's, whereby resolution by thetechniques to be discussed of two Tg's is not possible."

W. J. MacKnight et al., in Polymer Blends, D. R. Paul and S. Newman, p.188, Academic press, New York, NY. (1978) state:

"Perhaps the most unambiguous criterion of polymer compatibility is thedetection of a single glass transition whose temperature is intermediatebetween those corresponding to the two component polymers."

In this passage, it is clear that by compatibility the authors meanmiscibility, i.e., single phase behavior. See, for example, thediscussion in Chapter 1 by D. R. Paul in the same work. The abovereferences and related application are hereby incorporated by reference.

However, the miscible blends disclosed in this application are one phasebased on them having a single glass transition temperature giving theresulting blends improved chemical resistance compared to the immisciblemultiphase blends having similar constituents. Further, the miscibleblends show improved thermal and optical performance over immiscibleblends. This is attributable to discovering that select imide containingpolymers having an isopropylidene group are miscible with biphenylcontaining polysulfones. Herein, the term "polyimide" refers to polymerscontaining the following linkage: ##STR1## or mer unit.

SUMMARY OF THE INVENTION

This invention relates to a miscible blend of a poly(aryl sulfone) and apolyimide or amide-imide comprising: (a) poly(aryl sulfone) containingthe following unit: ##STR2## and (b) polyimide or amide-imide containingthe following unit: ##STR3##

This invention also relates to a process for producing a miscible blendof biphenyl containing poly(aryl sulfone), and isopropylidene and imidecontaining polymer comprising adding the monomers used to form thelatter polymer to the poly(aryl sulfone) in a vented extruder.

This invention further relates to a polyimide of the following formula:##STR4##

DETAILED DESCRIPTION OF THE INVENTION

Applicants disclose a method of improving the flow of polyimides (PI)and amide-imides (PAI) while at the same time improving the chemicalresistance of poly(aryl sulfones) (PAS) by alloying the two polymerstogether. A major factor limiting the applicability of the alloyingapproach is that the majority of polymer alloys are not miscible. Thatis, the alloys are two-phase; and the continuous phase is usually thelower viscosity component. Thus, immiscible blends will likely be apoly(aryl sulfone) filled with the polyimide or amide-imide component asinclusions. Such a morphology generally results in an improvement inflow (e.g. reduced viscosity). However, the chemical resistance of suchan alloy will be closer to that of the continuous phase than to theinclusions and may be expected to be poor. Additionally, in the eventthe T_(g) s of the two components are significantly different, the upperuse temperature of the alloy will not be significantly higher than thatof the lower T_(g) constituent. In the case of continuous fibercomposites wherein the alloy is the matrix resin, the reason for this isthat a high matrix modulus is necessary to prevent buckling of carbonfibers when a composite is loaded in compression. An immiscible blendhas two T_(g) s (usually near those of the constituents); and at eachT_(g), the matrix modulus drops significantly. If such a blend is usedas the composite matrix, then the useful temperature range of thecomposite is limited to the lower T_(g).

It has been discovered unexpectedly that a select group of poly(arylsulfones) is miscible with a select group of polyimides andamide-imides. The poly(aryl sulfone) must contain biphenyl linkageswhile the polyimides or amide-imides must contain isopropylidenelinkages. These blends show markedly improved chemical resistance and asingle T_(g) intermediate to those of the constituents resulting fromtheir miscible character. Thus, the upper use temperature of the alloymay be significantly improved over that of the lower T_(g) constituent.Further, by reducing the T_(g) of the higher T_(g) constituent, it istypically more processable. As a consequence of this, these alloys canbe used as injection moldable thermoplastic materials having improvedflow and toughness characteristics as well as better chemicalresistance.

The components of the miscible blend of imide containing polymers withpoly(aryl sulfones) will be discussed below. Also to be discussed is theneed or criticality of the mixture to exhibit a negative miscibilityfactor.

The poly(aryl sulfone)s which are suitable for use in the inventioncontain at least one biphenyl unit in the structure. The presence of thebiphenyl unit in the poly(aryl sulfone) is critical to obtainmiscibility between the poly(aryl sulfone) and the polyimide.

Poly(aryl sulfone) polymers are characterized by inherently high heatdistortion temperatures, excellent dimensional stability, creepresistance, low loss AC dielectric properties, and high mechanicalstrength as shown below.

    ______________________________________                                        Typical Properties of Poly(aryl sulfone) Resins                               Property          Units     Typical Range                                     ______________________________________                                        Tensile Strength  psi       12,500-15,000                                     Elongation to Break                                                                             %         >40                                               Tensile Modulus   psi          300-400,000                                    Flexural Strength psi       13,000-20,000                                     Heat Deflection Temperature                                                                     °C.                                                                              170-250                                           Density           gm/cc     1.2-1.4                                           AC Dielectrics                                                                Dielectric Constant                                                           60 HZ             --        3.0-4.0                                           1 KHZ             --        3.0-4.0                                           1 MHZ             --        3.0-3.5                                           Dissipation Factor                                                            60 Hz             --        0.0005-0.005                                      1 KHZ             --        0.0005-0.003                                      1 MHZ             --        0.004-0.01                                        Dielectric Strength                                                                             Volts/mil 350-550                                           1/8" specimen                                                                 ______________________________________                                    

Poly(aryl sulfone) polymers are easily processed utilizing standardinjection molding machinery and practice. Prior to molding, resinsshould be dried to obtain optimum performance in a dehumidified hopperdrier or circulating air oven.

The rheological characteristics of poly(aryl sulfone) polymers provideexcellent flow for filling thin and intricate wall sections typicallyencountered in injection molding. The polymers process readily at stocktemperatures in the 550°-750° F. range. Mold temperatures of 150°-400°F. are typically used.

The poly(aryl sulfone) may be random or may have an ordered structure.The poly(aryl sulfone)s, which are suitable for use in this invention,contain at least one biphenyl unit in the repeat unit. The preferredbiphenyl containing poly(aryl sulfone) contains the repeating unit:##STR5## where X₁ and X₂ are independently --O--, ##STR6## --SO₂ --,--NHCO--, CH₃ -- ##STR7## or a direct bond with the proviso that atleast one of X₁ or X₂ is a direct bond, and R, S and T are independently0 or 1; with the proviso that at least one of R or S is 1.

The preferred poly(aryl sulfones) include those having the followingreoccurring units: ##STR8##

Examples of commercially available biphenyl containing poly(arylsulfones) are the polymers known as Radel R and Radel C sold by AmocoPerformance Products, Inc. of Ridgefield, Conn.

The poly(aryl sulfone)s are produced by methods well known in the artsuch as those described in U.S. Pat. Nos. 3,634,355; 4,008,203;4,108,837 and 4,175,175, hereby incorporated by reference.

The preferred method of preparation, herein referred to as method A,involves the reaction of a dihydric phenol with a dihalobenzenoidcompound in substantially equal molar amounts in a mixture of alkalimetal carbonates and an aprotic solvent. The ratio of reactive halogengroups in the dihalobenzenoid compound to hydroxyl groups in thedihydric phenol is preferably from 0.98 to 1.02. Preferreddihalobenzenoid compounds include 4,4'dichlorodiphenylsulfone (DCDPS)and 4,4'-Bis[(4-chlorophenylsulfonyl)] 1,1'-biphenyl (BCPSB). Preferreddihydric phenols include 4,4'-dihydroxybiphenyl (BP),4,4'-dihydroxydiphenylsulfone (Bis-S), 1,4-dihydroxybenzene (HQ), andBis(4-hydroxyphenyl) 1-methylethylidene (Bis A).

The poly(aryl sulfones) are prepared by contacting substantiallyequimolar amounts of the dihydric phenols and dihalobenzenoid compoundswith from about 0.5 to 1.0 mole of an alkali metal carbonate per mole ofhydroxyl group in a solvent mixture comprising a solvent which forms anazeotrope with water to maintain the reaction medium at substantiallyanhydrous conditions during polymerization.

The reaction of the mixture is kept at from about 120° to about 180° C.for about 1 to 5 hours, then raised and kept at about 200° to 250° C.for about 1 to 10 hours. The reaction is carried out in an inertatmosphere, e.g., nitrogen, at atmospheric pressure. The poly(arylsulfone) may be recovered by conventional techniques such ascoagulation, solvent evaporation, and the like. The resultant polymershave reduced viscosities in the range from 0.4 to 1.5 dl/g, as measuredin N-methylpyrolidone at 25° C.

The other component of the blend is a polyimide or amide-imide thatcontains an isopropylidene group. The isopropylidene group is criticalto the miscibility of the blend constituents of this invention.Polyimides or amide-imides are characterized by the presence of thephthalimide structure in the polymer backbone: ##STR9##

Polyimides are very rigid polymers which sometimes lack the inherenttoughness needed to compete in those uses which require elevatedtemperature resistance and good impact strength. The lack of matrixtoughness can cause problems when molding thick cross-sectional parts.The art has been looking for improvements in the impact resistance andtoughness of these polymers but it is essential that the additive notsignificantly impair their thermal and strength properties, particularlytheir heat deflection temperatures, tensile strengths, and chemicalresistances.

The polyimides which are suitable for use in this invention comprisethose containing the following repeating units: ##STR10## wherein X₃,X₄, X₅ and X₆ are independently --O-- ##STR11## --SO₂ --, --NHCO--,##STR12## or a direct bond with the proviso that at least one isisopropylidene; and U, V and W are independently 0 or 1 with the provisothat at least one of U or V is 1.

The polyamide-imides which are suitable for use in this inventioncomprise those containing the following repeating units: ##STR13##wherein X₄, X₅, X₆, U, V and W are as defined above.

The preferred polyimides comprise those having the following recurringunits: ##STR14## wherein X₇ can be ##STR15## --SO₂ --, ##STR16## --O--or a direct bond.

The preferred polyamide-imides also comprise those having the followingrecurring units: ##STR17##

The polyimides of this invention may be made by methods well known inthe art such as those described in U.S. Pat. No. 4,713,438, herebyincorporated by reference. They are preferably prepared by the reactionof a dianhydride (or mixture of dianhydrides) with a diamine (or mixtureof diamines) in substantially equimolar amounts in a solvent followed bychemical dehydration of the intermediate poly(amide-acid), hereafterreferred to as Method B. Preferred dianhydrides include 1,2,4,5-benzenetetracarboxylic anhydride (PMDA), bis(4-phthalic anhydride)1-methylethylidene (IPAN), 3,3',4,4'-biphenyltetracarboxylic anhydride(BPDA), 3,3',4,4'-diphenylether tetracarboxylic anhydride (OPAN) and3,3',4,4'-benzophenone tetracarboxylic anhydride (BTDA). Preferreddiamines include 4,4'-(1-methylethylidene)bisaniline (BAA),4,4'-[1,4-phenylene bis (1-methyl ethylidene)] bisaniline (BAP),bis(4-amino phenoxy-4-phenyl) 1-methylethylidene (BAPP),4,4'-diaminodiphenylether (OBA), and 1,3-diaminobenzene (MPD).

The solvents useful in the solution polymerization process forsynthesizing the polyamide-acid compositions are the organic solventswhose functional groups do not react with either of the reactants (thediamines or the dianhydrides) to any appreciable extent. In addition tobeing inert to the system, and preferably, being a solvent for thepolyamide-acid, the organic solvent must be a solvent for at least oneof the reactants, preferably for both of the reactants. The normallyliquid organic solvents of the N,N-dialkylcarboxylamide class are usefulas solvents in the process. The preferred solvents are the lowermolecular weight members of this class, particularlyN,N-dimethylformamide and N,N-diethylacetamide. Other useful solventsare N,N-diethylformamide, N,N-diethylacetamide,N,N-dimethylmethoxyacetamide, N-methyl caprolactam, and the like. Othersolvents which may be used include dimethylsulfoxide,N-methyl-2-pyrrolidone, tetramethyl urea, pyridine, dimethylsulfone,hexamethyl-phosphoramide, tetramethylene sulfone, formamide,N-methyl-formamide, butyrolactone and phenols such as m-cresol. Thesolvents can be used alone, in combinations, or in combination withpoorer solvents such as benzene, benzonitrile, dioxane, xylene, tolueneand cyclohexane.

Another group of solvents that are very useful for the preparation ofpolyimides as well as of poly(amide-imides) are the diaryl sulfones anddiaryl ketones; they may be used alone or in combination with othersolvents such as the hydrocarbons, chlorinated hydrocarbons, etc.Typical representatives are diphenyl sulfone and benzophenone. Thesesolvents are of interest because they allow for the use of hightemperatures and are, therefore, adequate in cases where the aminereaction reactivity is low; or in cases where low solubility of thepolymer is encountered. In both instances, use of higher reactiontemperatures may be necessary. Also, the thermal cyclization of thepoly(amide-acids) to the corresponding polyimides can be performed inthe same solvent by simply increasing the temperature to the requiredlevel. The same is feasible with phenolic solvents such as the cresols;the diaryl sulfones and ketones have the added advantage of lowtoxicity, however.

For most combinations of diamines and dianhydrides falling within thedefinition given above, it is possible to form compositions of 100%poly(amide-acid) by conducting the reaction below 100° C. However,temperatures up to 175° C. and higher may be tolerated to provideshapeable compositions.

The degree of polymerization of the poly(amide-acid) is subject todeliberate control. The use of equal molar amounts of the reactantsunder the prescribed conditions provides poly(amide-acids) of highmolecular weight. The use of either reactant in large excess limits theextent of polymerization. In addition to using an excess of one reactantto limit the molecular weight of the poly(amide-acid), a chainterminating agent such as phthalic anhydride may be used to "cap" theends of the polymer chains. Typical useful capping agents are less than5 wt. % of monoanhydrides or monoamines such as phthalic anhydride,aniline, p-methylaniline, and the amine and anhydride shown below:##STR18##

In the preparation of the poly(amide-acid), it is desired that themolecular weight be such that the inherent viscosity of the polymer isat least 0.1, preferably 0.3-1.5. The inherent viscosity is measured at25° C. at a concentration of 0.5% by weight of the polymer in a suitablesolvent such as N-methylpyrolidone.

The quantity of organic solvent used in the process need only besufficient to dissolve enough of one reactant, preferably the diamine,to initiate the reaction of the diamine and the dianhydride. It has beenfound that the most successful results are obtained when the solventrepresents at least 60% of the final solution. That is, the solutionshould contain 0.05-40% of the polymeric component.

The second step of the process is performed by treating thepoly(amide-acid) with a dehydrating agent, alone or in combination witha tertiary amine, such as acetic anhydride or an aceticanhydride-pyridine mixture. The ratio of acetic anhydride to pyridinecan vary from just above zero to infinite mixtures.

In addition to acetic anhydride, lower fatty acid anhydrides andaromatic monobasic acid anhydrides may be used. The lower fatty acidanhydrides include propionic, butyric, valeric, and the like.

The aromatic monobasic acid anhydrides include the anhydride of benzoicacid and those of the following acids: o-, m-, and p-toluic acids; m-and p-ethyl benzoic acids; p-propyl benzoic acid; p-isopropyl benzoicacid; anisic acid; o-, m- and p-nitro benzoic acids; o-, m-, and p-halobenzoic acids; the various dibromo and dichloro benzoic acids; thetribromo and trichloro benzoic acids; and the like.

Tertiary amines having approximately the same activity as the preferredpyridine can be used in the process. These include isoquinoline,3,4-lutidine, 3,5-lutidine, 4-methyl pyridine, 3-methyl pyridine,4-isopropyl pyridine, N,N-dimethyl benzyl amine, 4-benzyl pyridine, andN,N-dimethyl dodecyl amine. These amines are generally used from 0.3 toequimolar amounts with that of the anhydride converting agent. Trimethylamine and triethylene diamines are much more reactive, and therefore aregenerally used in still smaller amounts. On the other hand, thefollowing operable amines are less reactive than pyridine:2-ethylpyridine, 2-methyl pyridine, triethyl amine, N-ethyl morpholine,N-methyl morpholine, diethyl cyclohexylamine, N,N-dimethylcyclohexylamine, 4-benzoyl pyridine, 2,4-lutidine, 2,6-lutidine and2,4,6-collidine, and are generally used in larger amounts.

Dehydration of the poly(amide-acid) to form the polyimide, that isimidization, can also be performed by heating the poly(amide-acid)solution to temperatures at or above 200° C. at reflux to remove thewater which is a by-product of the reaction. Additionally, a catalyst,such as p-toluenesulfonic acid, and/or an azcotrophing agent, such asmonochlorobenzene, can be added to assist the thermal imidization.

A novel class of solvents for the polymerization of polyimides is thepoly(arylsulfone)s of the present invention. The combination of thediamines and dianhydride can be added to the molten poly(arylsulfone) attemperatures between 200° and 400° C.; preferably between 300° and 380°C. While not generally considered solvents for the poly(amide-acid)intermediates, these poly(arylsulfones) are by virtue of being miscibletrue solvents for the polyimides of this invention. However, because thereaction between the aromatic amine and anhydride end groups takes placeat such high temperatures, the amide-acid intermediate is never formedand thus the poly(arylsulfone) performs all of the desired functions ofa good solvent including solubilization of the reaction product. Becauseof the relatively high viscosity of the resulting solution, the reactioncan be best accomplished in an extruder or other device capable ofconveying viscous polymer solutions. Such devices are known in the artand are described in any good text on polymer processing such as J. L.Throne, "Plastics Process Engineering," Marcel Dekker, New York, 1979,hereby incorporated by reference. The extruder or other device shouldpreferably be vented to provide for the removal of the by products(water) of the reaction. This process has several advantages. Firstly,because the processing takes place above 200° C., imidization occursspontaneously and not in a separate step after the formation of thepoly(amide acid). Secondly, the solvent (i.e., the poly(arylsulfone))does not have to be removed via a recovery step after the polymerizationis complete. Lastly, the blend is formed in situ and not during asubsequent compounding step. The elimination of these three intermediatesteps results in considerably better economics.

The resulting polyimides of the instant invention can be homopolymers,random copolymers, and block copolymers. They have reduced viscositiesas measured in N-methylpyrolidone at concentrations of 0.5% by weight at25° C. between 0.1 and 1.5 dl/g and higher.

The polyamide-imides of this invention may be made by methods well knownin the art such as those described in U.S. Pat. No. 4,713,438.

The preparation of the poly(amide-imides) is preferably performed usingreactions that are similar to those discussed for the preparation of thepolyimides. This method of preparation will be referred to as Method C.Typically a tricarboxylic acid monoanhydride or derivative thereof isreacted with a diamine (or mixture of diamines) as shown below and asdescribed in, for example, Japanese Patent Application Nos. 61/126,136and 61/126,137, hereby incorporated by reference. ##STR19##

Preferred tricarboxylic acid monoanhydride derivatives include1,2,4-benzenetricarboxylic anhydride and 1,2,4-benzenetricarboxylicanhydride acid chloride. The preferred diamines include those describedfor the polyimides.

Typical aprotic solvents which are the same as those used forpolyimides, e.g., N,N-dimethylacetamide or N-methylpyrrolidone, and thelike are useful. In another embodiment, these polymers can be preparedvia the reaction of diisocyanate and tricarboxylic acid monoanhydride.The reaction is base-catalyzed. See for example, Japanese PatentApplication No. 61/14,218, hereby incorporated by reference. It isillustrated below: ##STR20##

Experimental details are generally the same as those described for thecorresponding preparation of the polyimides.

The resulting polyamide-imides of the instant invention can behomopolymers, random copolymers, and block copolymers. They have reducedviscosities as measured in N-methylpyrrolidone at concentrations of 0.5%by weight at 25° C. between 0.1 and 1.5 dl/g and higher.

Not all blends containing the components mentioned above are miscible.However, a novel way has been determined to select those that aremiscible with each other. It has been determined that the miscibilityfactor for the components must be negative for the components to bemiscible and to form a polymer with a single glass transitiontemperature.

As mentioned previously, polymer miscibility cannot be predicted. Thereis recent evidence that once several examples are found where polymersof a class 1 are miscible with polymers of a class 2, then the phasebehavior of blends of polymers of class 1 and polymers of class 2 can becorrelated with structure. The net result is that a mathematicalinequality can be written which correctly predicts when other polymerschosen from class 1 and class 2 are miscible. There is evidence that themiscibility of two polymers composed of several different types of merunits can be correlated by an equation of the type: ##EQU1## where F_(c)is a small positive number (or zero), the φ_(i) ^(K) are related to thenumber of mers of type i in polymer K, and the B_(ij) represents theinteraction energy between mers of type i and j. A mer is a smallsubstructural component of a polymer repeat unit. For example, in Paul,et al., Polymer 25, pp. 487-494 (1984), hereby incorporated byreference, the miscibility of the polyhydroxy ether of bisphenol A issuccessfully correlated with a series of aliphatic polyesters using(equation 10 in the above reference).

    O>B.sub.13 φ.sub.1 '+B.sub.23 φ.sub.2 '-B.sub.12 φ.sub.1 'φ.sub.2 '                                            (2)

Equation (2) is equivalent to equation (1) if the following change ofnotation is made:

F_(c) =O

φ'₁ =φ₁ ¹

φ'₂ =φ₂ ¹

φ₃ ² =1

and all other φ_(i) ^(K) =0.

In this case, the φ_(i) ^(K) are taken to be the volume fraction mer iin polymer K. The B_(ij) were essentially taken as adjustable parametersrepresenting the enthalpy of interaction between group i and j. Paul andcoworkers considered the polymer blend system to be made up of threegroups, or mers:

(i) --CH₂ -- and

(ii) ##STR21## which make up the aliphatic polyesters, and ##STR22##which makes up the polyhydroxy ether.

Kambour, et al, Macromolecules, 16, pp. 753-757 (1983) used a similarequation to correlate the miscibility of poly(styrene-co-bromostyrene)with poly(xylenyl co-bromoxylenyl-ether), hereby incorporated byreference. In the case where polymer 1 contained only mers of type i andpolymer 2 contained mers of type j and k, the condition of miscibilitythat is arrived at is (see equation 4 on page 756 of the above citedwork):

    X.sub.AB.sup.C >(1-Å.sub.C)X.sub.ij +Å.sub.c (X.sub.ik)-Å.sub.c (1-Å.sub.c)X.sub.kj                                   ( 3)

Note the mistake in the third term of equation 4 in Kambour, et al,which is corrected in equation (3) above. Equation (3) is seen to beidentical with equation (1) if the following change of notation is made:

F_(c) =X_(AB) ^(C)

X_(c) =φ_(j) ²

(1-X_(c))=φ_(K) ²

φ_(i) ¹ =1

All other φ_(i) ^(K) =0.

X_(ij) =B_(ij) for all i j.

In this instance, Kambour has taken the φ_(i) ^(K) to be the molefraction mer i in polymer K. Again the B_(ij) were taken to beadjustable parameters.

There is a precedent, then, for correlating miscibility using equation(1). We have seen that the φ_(i) ^(K) may be interpreted as volumefractions or mole fractions. Prausnitz, et al, in the Properties ofGases and Liquids, Third Edition, published by McGraw Hill Book Co., NewYork, N.Y. (1977), hereby incorporated by reference, recommend the useof molecular area fractions in equations similar to equation (1) (SeeChapter 8 in Prausnitz, et al). They recommend the use of the groupcontribution method developed by A. Bondi in the Physical Properties ofMolecular Liquids, Crystals and Glasses, Chapter 14, published by JohnWiley and Sons, New York, N.Y. (1968), hereby incorporated by reference,for the estimation of the surface area of mer units.

It has been found that when poly(aryl sulfones) are miscible with imidecontaining polymers, the miscible blend comprises separately madebiphenyl containing polysulfones with isopropylidene based polyimides oramide-imides formed into an intimate moldable mixture by physicalmethods such as melt extrusion.

Miscible combinations have been correlated for poly(aryl sulfone) andpolyimide or amide-imide alloys. It is highly probable that they will bemiscible if the Miscibility Factor (MF) defined by the followingequation is less than 0.05: ##EQU2## where φ_(K) ^(l) is the areafraction mer K in polymer l (l=1 (PAES), 2(PI, PAI)). The mers arechosen from the list in Table I where their estimated molar surfaceareas are also given. The miscibility factor in Equation (4) may bethought of as a function of the composition of the PAES, designated byφ₁ ¹, φ₂ ¹, φ₃ ¹, . . . φ_(m) ¹, and the PI or PAI, by φ₁ ², φ₂ ², φ₃ ²,. . . φ_(n) ².

If this function is less than 0.05, polymers 1 and 2 will be completelymiscible. If this function is greater than 0.05, then polymers 1 and 2will be for all practical purposes immiscible. Of course, when thisfunction is near 0.05 then polymer 1 and 2 are likely to be partiallymiscible. The quantity φ_(K) ^(l) may be calculated if the molefractions of the various mers in polymer l are known. If X_(i) is themole fraction mer i in polymer l, then ##EQU3## where A_(i) is the molarsurface area of mer i (given in Table I) and the sum is over all typesof mers which are given in Table I.

The blends of this invention are at least partially miscible.Preferably, the blends of this invention are miscible in allproportions. Preferably, the blends contain from about 2 to about 98,more preferably, the blends contain from about 15 to about 85 weight %of the poly(aryl sulfone), the balance being the polyimide oramide-imide constituent. The individual concentrations are readilychosen by those skilled in the art.

The blends of this invention are prepared by conventional mixingmethods. For example, the polymer components are mixed with each otherand any other optional ingredients in powder or granular form in anextruder. The mixture is extruded into strands. The strands are choppedinto pellets; the pellets are molded into the desired article.

Additives which may be used with the thermoplastic alloy includereinforcing and/or non-reinforcing fillers such as wollastonite,asbestos, talc, alumina, clay, mica, glass beads, fumed silica, gypsum,graphite powder, molydenum disulfide and the like; and reinforcementfibers such as aramid, boron, carbon, graphite, and glass. Glass fiberis the most widely used reinforcement in the form of chopped strands,ribbon, yarn, filaments, or woven mats. Mixtures of reinforcing andnon-reinforcing fillers may be used, such as a mixture of glass fibersand talc or wollastonite. These reinforcing agents are used in amountsof from about 10 to about 80 weight percent, whereas the non-reinforcingfillers are used in amounts of up to 50 weight percent. Other additivesinclude stabilizers, pigments, flame retardants, plasticizers,processing aids, coupling agents, lubricants, mold release agents, andthe like. These additives are used in amounts which achieve the desiredresult. A particularly useful additive, especially when either of theblend constituents contains a carbonyl linkage, is a hydrate such asthose described in U.S. patent application Ser. No. 07/291,966, filedDec. 30, 1988, now U.S. Pat. No. 4,963,627, entitled Injection MoldableBlends of Poly(Etherketones) and Poly Amide-Imides to Smyser et al.

EXAMPLES

The following examples serve to give specific illustrations of thepractice of this invention but are not intended to limit the scope ofthis invention. They are exemplary, not exclusive. The examples show theunexpected discovery noted above. Table II compiles the polymers used inthe following blending experiments along with their structures in termsof φ₁ ^(K), φ₂ ^(K) . . . φ₇ ^(K).

Example 1

A 50/50 blend of PAES-I (Radel R5000 obtained from Amoco PerformanceProducts, RV=0.56 dl/g as measured in 0.5% N-methylpyrolidone (NMP)solution at 25° C.) and PAI-I, as defined in Table II, (I.V.=0.90 dl/gas measured in 0.5% NMP solution at 25° C.) are melt mixed in aBrabender mixing head at 360° C. and 50 RPM for five minutes. The blendis compression molded into a 4×4×0.02 inch plaque at about 350° C. Themolded plaque is observed to be transparent with low haze. The plaque istested for tensile strength, 1% secant modulus and elongation at breakaccording to a procedure similar to ASTM D-638. The pendulum impactstrength of the plaque is also measured.

Pendulum impact strength is measured as follows. A steel pendulum isused, cylindrical in shape with a diameter of 0.83 inch and weighing1.562 pounds. The striking piece, mounted almost at the top of thependulum, is a cylinder 0.3 inch in diameter. Film specimens, 4 incheslong, 0.125 inch wide and about 1 to 30 mils thick are clamped betweenthe jaws of the tester so that the jaws are spaced one inch apart. The0.125 inch width of the film is mounted vertically. The pendulum israised to a constant height to deliver 1.13 foot pounds at the specimen.When the pendulum is released, the cylindrical striking piece hits thespecimen with its flat end, breaks the film, and travels to a measuredheight beyond. The difference in the recovery height (i.e., thedifference in the potential energy of the pendulum at the maximum pointof the upswing), represents the energy absorbed by the specimen duringthe rupture. The impact strength, expressed in foot-pounds per cubicinch, is obtained by dividing the pendulum energy loss by the volume ofthe specimen.

The modulus-temperature and resilience-temperature relationship for theblend is determined using an Instron testing device equipped with asample chamber capable of being heated to 400° C. at 1.6° C./min. Fromthis information, the (Tg or Tgs) of the blend is (are) extracted as theminimum (minima) in the resilience-temperature curve at a strain rate of0.2 inches/minute. See the discussion in Olabisi et al, Polymer-PolymerMiscibility, pp. 126-127, Academic Press, New York (1979), for adiscussion of the modulus-resilience method. The results of the testingare shown in Table III.

Example 2 (Comparative)

Example 1 is repeated except PAES-II (Victrex PES-200P obtained from ICIAmericas RV=0.5 dl/g as measured in 0.5% NMP solution at 25° C.) issubstituted for PAES-I and the composition is 60/40 PAES-II/PAI-I. Themolded plaque is translucent with noticeable haze. The results of thetesting are given in Table III.

                  TABLE I                                                         ______________________________________                                        MERS                                                                                   Surface Area                                                         Index    (cm.sup.2 /mole)                                                                         Structure of Mer                                          ______________________________________                                        1        4.96 × 10.sup.9                                                                     ##STR23##                                                2        7.02 × 10.sup.9                                                                     ##STR24##                                                3        8.84 × 10.sup.9                                                                     ##STR25##                                                4        4.6  × 10.sup.9                                                                     ##STR26##                                                5        6.02 × 10.sup.9                                                                     ##STR27##                                                6        7.06 × 10.sup.9                                                                     ##STR28##                                                7        7.01 × 10.sup.9                                                                     ##STR29##                                                ______________________________________                                    

                                      TABLE II                                    __________________________________________________________________________    POLYMERS USED IN BLENDING EXPERIMENTS                                         __________________________________________________________________________                      Poly(aryl sulfones)                                         Dihalobenzenoid   Dihydric  Method of                                                                           Composition of Resultant Poly(aryl                                            sulfone)                                    PAES                                                                              Compound(s)                                                                            Mole %                                                                             Phenol(s)                                                                          Mole %                                                                             Preparation                                                                         φ.sub.1.sup. 1                                                               φ.sub.2.sup. 1                                                               φ.sub.3.sup.                                                                 φ.sub.4.sup.                                                                 φ.sub.5.sup.                                                                 φ.sub.6.sup.                                                                 φ.sub.7.sup.          __________________________________________________________________________                                                        1                         I   DCDPS    100  BP   100  A     0.46                                                                             0.33                                                                             0  0.21                                                                             0  0  0                         II  DCDPS    100  BisS 100  A     0.41                                                                             0.59                                                                             0  0  0  0  0                         III DCDPS    100  BisA 100  A     0.39                                                                             0.27                                                                             0.34                                                                             0  0  0  0                         IV  DCDPS    100  HQ    80  A     0.56                                                                             0.39                                                                             0  0.05                                                                             0  0  0                                           BP    20                                                    V   BCPSB    100  HQ    50  A     0.32                                                                             0.46                                                                             0  0.22                                                                             0  0  0                                           BP    50                                                    VI  DCDPS    100  BisS  75  A     0.45                                                                             0.55                                                                             0  0  0  0  0                                           HQ    25                                                    VII BCPSB    100  BP   100  A     0.30                                                                             0.42                                                                             0  0.28                                                                             0  0  0                         __________________________________________________________________________    Triacid an-                                                                   hydride acid                                                                  chloride or       Polyamide-imides                                            dianhydride or              Method of                                                                           Composition of Resultant                                                      Polyamide-imide                             PAES                                                                              diacid Chloride                                                                        Mole %                                                                             Diamine                                                                            Mole %                                                                             Preparation                                                                         φ.sub.1.sup.2                                                                φ.sub.2.sup. 2                                                               φ.sub.3.sup.2                                                                φ.sub.4.sup.2                                                                φ.sub.5.sup.2                                                                φ.sub.6.sup.2                                                                φ.sub.7.sup.2         __________________________________________________________________________    I   4-TMAC*  100  BAP  100  C     0  0  0.56                                                                             0  0  0.22                                                                             0.22                      II  4-TMAC    65  BAPP 100  C     0.30                                                                             0  0.27                                                                             0  0  0.29                                                                             0.14                          PMDA      35                                                              III 4-TMAC   100  BAA  100  C     0  0  0.38                                                                             0  0  0.31                                                                             0.31                      IV  4-TMAC   100  BAPP 100  C     0.30                                                                             0  0.28                                                                             0  0  0.21                                                                             0.21                      V   4-TMAC   100  OBA   70  C     0.20                                                                             0  0  0  0  0.40                                                                             0.40                                        MPD   30                                                    VI  4-TMAC    50  MPD  100  C     0  0  0  0  0  0.25                                                                             0.75                          IAC**     50                                                              __________________________________________________________________________                      Polyimides                                                                              Method of                                                                           Composition of Resultant Polyimide          PI  Dianhydride                                                                            Mole %                                                                             Diamine                                                                            Mole %                                                                             Preparation                                                                         φ.sub.1.sup.2                                                                φ.sub.2.sup. 2                                                               φ.sub.3.sup.2                                                                φ.sub.4.sup.2                                                                φ.sup.5.sup.2                                                                φ.sub.6.sup.2                                                                φ.sub.7.sup.          __________________________________________________________________________                                                        2                         I   IPAN     100  BAA  100  B     0  0  0.56                                                                             0  0  0.44                                                                             0                         II  IPAN     100  BAP  100  B     0  0  0.65                                                                             0  0  0.35                                                                             0                         III IPAN     100  OBA  100  B     0.18                                                                             0  0.32                                                                             0  0  0.50                                                                             0                         IV  IPAN     100  MPD  100  B     0  0  0.39                                                                             0  0  0.61                                                                             0                         V   BPDA     100  BAA  100  B     0  0  0.32                                                                             0.17                                                                             0  0.51                                                                             0                         VI  BPDA     100  BAP  100  B     0  0  0.48                                                                             0.13                                                                             0  0.39                                                                             0                         VII BTDA     100  BAA  100  B     0  0  0.30                                                                             0  0.21                                                                             0.49                                                                             0                         VIII                                                                              BTDA     100  BAP  100  B     0  0  0.47                                                                             0  0.16                                                                             0.37                                                                             0                         __________________________________________________________________________     *Trimethylacetamide                                                           **Isophthalic acid chloride                                              

Example 3 (Comparative)

A 50/50 blend of PAES-III (Udel P-1700 obtained from Amoco PerformanceProducts, RV=0.5 dl/g as measured in 0.5% CHCl₃ solution at 23° C.) andPAI-I is made by dissolving 3 grams of each in NMP to make a 10%solution. It is coagulated into an 80/20 water/methanol mixture andfiltered. The filtrate is reslurried in water and boiled for 5 hours,refiltered, and dried. The dry cake is compression molded as inExample 1. Its Tgs are determined as in Example 1 and are given in TableIII.

Controls A, B, C and D

PAES-I, PAES-II, PAES-III, and PAI-I are compression molded at about350° C. The moldings are tested as in Example 1. The results of thetesting are given in Table III.

As can be seen, the blend of PAES-I and PAI-I is miscible by virtue ofits intermediate single Tg and transparency. Conversely, blends ofPAES-II or PAES-III with PAI-I are seen to be immiscible as two Tgs aredetected and by virtue of the poor optical properties of the blends.

Example 4

A 50/50 blend of PAES-I and PAI-II (I.V.=0.25 dl/g as measured in 0.5%NMP solution at 25° C.) is melt homogenized in a Brabender mixing headat 360° C. and 50 rpm. The blend is molded and tested as in Example 1with the exception that the Tg is determined using a PolymerLaboratories DMTA operating in tensile mode at 10 Hz and scanning at 5°C./min. The Tg is taken as the maximum in the tan δ curve. The resultsare given in Table III. The molding is transparent with little haze.

Example 5 (Comparative)

A 50/50 blend of PAES-III and PAI-II is melt homogenized in a Brabendermixing head at 360° C. and 50 rpm. The blend is molded and tested as inExample 4. The results are given in Table III. The molding istranslucent with significant haze.

Example 6 (Comparative)

A 50/50 blend of PAES-IV (RV=0.92 as measured in a 1% NMP solution at25° C.) and PAI-II is melt homogenized in a Brabender mixing head at360° C. and 50 rpm. The blend is molded and tested as in Example 4. Theresults are given in Table III. The molding is translucent withconsiderable haze.

Controls E and F

PAI-II (I.V.=0.79 dl/g as measured in 0.5% NMP solution at 25° C.; sameas used in Example 4, except solid state advanced to a higher MW) andPAES-IV are compression molded into 4×4×0.20 inch plaques at 360° C. andtested as in Example 4. The results are given in Table III.

                                      TABLE III                                   __________________________________________________________________________    BLEND PROPERTIES                                                                                                    Pendulum                                                      Tensile         Impact                                                        Strength                                                                           Elongation                                                                          Modulus                                                                            Strength                                                                            Tg(s)                             Example                                                                             Component I                                                                           Component II                                                                          (psi)                                                                              (%)   (ksi)                                                                              (ft-lb/in.sup.3)                                                                    (°C.)                      __________________________________________________________________________    1     50% PAES-I                                                                            50% PAI-I                                                                             11,400                                                                             16    236  121   242                               2     60% PAES-II                                                                           40% PAI-I                                                                             12,700                                                                               8.4 275   72   232,278                           3     50% PAES-III                                                                          50% PAI-I                                                                             --   --    --   --    185,265                           Control A                                                                           100% PAES-I                                                                           --       9,920                                                                             75    230  184   223                               Control B                                                                           100% PAES-II                                                                          --      12,000                                                                             26    245  116   229                               Control C                                                                           100% PAES-III                                                                         --       9,710                                                                             40    234  152   185                               Control D                                                                           100% PAI-I                                                                            --      14,300                                                                             13    289   97   270                               4     50% PAES-I                                                                            50% PAI-II                                                                            11,200                                                                             17    255  238   235                               5     50% PAES-III                                                                          50% PAI-II                                                                            --   --    --   --    184,236                           6     50% PAES-IV                                                                           50% PAI-II                                                                            --   --    --   --    215,260                           Control E                                                                           100% PAI-II                                                                           --      --   --    --   --    245                               Control F                                                                           100% PAES-IV                                                                          --      --   --    --   --    210                               __________________________________________________________________________

Example 7

A 50/50 blend of PAES-I and PI-I (RV=0.60 dl/g as measured in 0.5% NMPsolution at 25° C.) is made by dissolving 2.5 grams of each indimethylacetamide (DMAC) at 25° C. to make a 20% solution. It iscoagulated in a Waring blender filled with a methyl alcohol/watermixture. The resultant coagulant is filtered and dried overnight undervacuum at 200° C. The next morning it is compression molded into a2×2×0.010 inch plaque at 360° C. The Tg of the plaque is measured usinga Polymer Laboratories DMTA operating in the tensile mode at 1 Hz andscanning at 3° C./min. The HDT of the blend at 264 psi is estimated asthe temperature where the modulus of the blend dropped to 100,000 psi assuggested by M. T. Takemori in the SPE Proceeding of ANTEC, pp. 216-219Apr. 24-27, 1978), hereby incorporated by reference. Results of thetesting are given in Table IV.

Example 8

A 50/50 blend of PAES-V (RV=0.57 dl/g as measured in a 1% NMP solutionat 25° C.) and PI-I is made and tested as in Example 7. The results aregiven in Table IV.

Example 9 (Comparative)

A 50/50 blend of PAES-VI (Radel A 400 obtained from Amoco PerformanceProducts, RV=0.48 dl/g as measured in 1.0% NMP solution at 25° C.) ismade and tested as in Example 7. The results are given in Table IV.

Controls A, G, H, I

PI-I and PAES-I, V and VI are compression molded into 4×4×0.02 inchplaques at 360°-380° C. The moldings are tested as in Example 7 and theresults are given in Table IV.

One of the advantages of a miscible blend as opposed to an immiscibleblend (in addition to transparency) is demonstrated in the last columnof Table IV. PAES-I and PAES-VI have similar Tgs and HDTs, yet theformer is miscible with PI-I while the latter is not. A 50/50 blend withPI-I increases the HDT of PAES-I by 32° C. to 246° C. while it increasesthe HDT of PAES-VI by only 8° C. to 224° C. A significant improvement inthe HDT of PAES-V, which is also miscible with PI-I, is observed onblending.

                  TABLE IV                                                        ______________________________________                                        BLEND PROPERTIES                                                                                              Tg(s)  HDT*                                   Example Component I Component II                                                                              (°C.)                                                                         (°C.)                           ______________________________________                                        7        50% PAES-I 50% PI-I    259    246                                    8        50% PAES-V 50% PI-I    283    263                                    9        50% PAES-VI                                                                              50% PI-I    227,277                                                                              224                                    Control A                                                                             100% PAES-I --          223    214                                    Control G                                                                             100% PI-I   --          292    281                                    Control H                                                                             100% PAES-V --          263    240                                    Control I                                                                             100% PAES-VI                                                                              --          225    216                                    ______________________________________                                         *Estimated at 264 psi.                                                   

Examples 10 through 35

The phase behavior of the blends of Examples 1 through 9 are summarizedin Table V. Further, the phase behavior of several additional 50/50blends of various poly(aryl sulfones) with various polyimides andamide-imides are also summarized in Table V as Examples 10 through 35.The blends are made by the same methods used to prepare Example 1through 9, except where noted. The blends are compression molded and theTg(s) of the moldings are determined by a) modulus/resilience, b) DMTAor c) DSC. The blends are judged to be miscible (immiscible) on thebasis of one (two) Tg(s) existing between (similar to) those of theconstituents. Only poly(aryl sulfones) containing biphenyl linkages arefound to be miscible with polyimides or amide-imides. Thus, biphenyllinkages in the poly(aryl sulfone) appear to be necessary. Further, thepolyimides or amide imides all contain an isopropylidene group. Imidegroups in conjunction with isopropylidene groups also appear to benecessary as no polyamide or amide-imide not containing anisopropylidene linkage is found to be miscible with a poly(arylsulfone).

The required proportions of biphenyl linkages in the PAES andisopropylidene linkages in the PI or PAI are determined by Equation 4.If the Miscibility Factor is less than 0.05 then the blend will verylikely be miscible in all proportions. If the Miscibility Factor is verynear 0.05, a borderline case exists and the blend may be miscible orimmiscible, or most likely partially miscible. Finally, if theMiscibility Factor is greater than 0.05 then the blend will very likelybe immiscible and not within the scope of this invention.

The last column in Table V gives the value of the Miscibility Factorcalculated for the particular polymer combination given in columns 2 and4. As can be seen, the Miscibility Factor is less than or equal to 0.05in every miscible example. Likewise, the Miscibility Factor is greaterthan or equal to 0.05 in every immiscible example. Note that when theMiscibility Factor is equal to 0.05, then the Example may be miscible(Example 18), immiscible (Example 32) or partially miscible (Example16). Thus the deviation of the Miscibility Factor from the value of 0.05is a measure of the blend compatibility.

                                      TABLE V                                     __________________________________________________________________________    Observed Phase Behavior of 50/50 Blends of Various Poly(aryl sulfones)        with Various Polyimides and Polyamide-imides                                                Biphenyl                                                                             Imide                                                                  Group in                                                                             Containing                                                                          Method of                                                                             Observed  Miscibility Factor               Example                                                                            PAES Compound                                                                          Repeat Unit                                                                          Compound                                                                            Forming Blend                                                                         Phase Behavior                                                                          of Equation.sup.4                __________________________________________________________________________     1   PAES-I   YES    PAI-I 2       Miscible  -0.01                             2   PAES-II  NO     PAI-I 2       Immiscible                                                                              0.07                              3   PAES-III NO     PAI-I 1       Immiscible                                                                              0.21                              4   PAES-I   YES    PAI-II                                                                              2       Miscible  0.04                              5   PAES-III NO     PAI-II                                                                              2       Immiscible                                                                              0.39                              6   PAES-IV  SOME   PAI-II                                                                              2       Immiscible                                                                              0.12                              7   PAES-I   YES    PI-I  4       Miscible  -0.21                             8   PAES-V   YES    PI-I  4       Miscible  -0.14                             9   PAES-VI  NO     PI-I  4       Immiscible                                                                              0.12                             10   PAES-VI  NO     PAI-III                                                                             1       Immiscible                                                                              0.27                             11   PAES-II  NO     PAI-III                                                                             1       Immiscible                                                                              0.27                             12   PAES-I   YES    PAI-III                                                                             1       Immiscible                                                                              0.29                             13   PAES-III NO     PAI-III                                                                             1       Immiscible                                                                              0.70                             14   PAES-VI  NO     PAI-II                                                                              2       Immiscible                                                                              0.21                             15   PAES-II  NO     PAI-II                                                                              2       Immiscible                                                                              0.23                             16   PAES-V   YES    PAI-II                                                                              2       Partially Miscible*                                                                     0.05                             17   PAES-VIII                                                                              YES    PAI-II                                                                              1       Miscible  0.01                             18   PAES-V   YES    PAI-IV                                                                              2       Miscible  0.05                             19   PAES-VI  NO     PAI-V 2       Immiscible                                                                              1.04                             20   PAES-II  NO     PAI-V 2       Immiscible                                                                              1.02                             21   PAES-VI  NO     PAI-VI                                                                              2       Immiscible                                                                              1.72                             22   PAES-II  NO     PAI-VI                                                                              2       Immiscible                                                                              1.65                             23   PAES-I   YES    PI-V  2       Immiscible                                                                              0.17                             24   PAES-V   YES    PI-V  2       Immiscible                                                                              0.23                             25   PAES-II  NO     PI-VI 2       Immiscible                                                                              0.29                             26   PAES-I   YES    PI-VI 2       Miscible  -0.08                            27   PAES-III NO     PI-VI 2       Immiscible                                                                              0.29                             28   PAES-I   YES    PI-IV 2       Immiscible                                                                              0.05                             29   PAES-I   YES    PI-VIII                                                                             2       Miscible  -0.13                            30   PAES-V   YES    PI-VIII                                                                             2       Miscible  -0.06                            31   PAES-II  NO     PI-II 2       Immiscible                                                                              0.14                             32   PAES-III NO     PI-II 3       Immiscible                                                                              0.05                             33   PAES-II  NO     PI-I  3       Immiscible                                                                              0.16                             34   PAES-I   YES    PI-III                                                                              2       Miscible  0.01                             35   PAES-VIII                                                                              YES    PI-III                                                                              1       Miscible  0.00                             __________________________________________________________________________     Methods of Forming the Blends                                                 1 = Solution Blend as in Example 3                                            2 = Melt blend made in Brabender as in Example 1                              3 = Solution Blend as in Example 3 Except methylene chloride was used as      the solvent instead of Nmethyl pyrolidone                                     4 = Solution Blend as in Example 7                                            *Blend determined to be partially miscible by transmission and scanning       electron microscopy. Electron dispers spectroscopy was used to contrast       the poly(aryl sulfone) rich phase. Tgs of the constituents were too close     together to determine phase behavior by mechanical or calorimetric            methods.                                                                 

Example 36

A 50/50 blend of PAES-I (RADEL R5000 obtained from Amoco PerformanceProducts, Inc.) and PAI-II (I.V.=0.30 dl/g as measured in 0.5% NMPsolution at 25° C.) is made in a one inch single screw (L/D=36) extruderat about 350° C. The extrudate is chopped into pellets, dried to removeabsorbed moisture and injection molded at about 340° C. into ASTM testspecimens. The molded blend is tested as shown in Table VI.

Example 37 (Comparative)

A 50/50 blend of PAES-II (Victrex 200P obtained from I.C.I. Americas,Inc.) and PAI-II (same as in Example 36) is made and tested as describedin Example 36. The results are given in Table VI.

Controls J and K

Pellets of the PAES-I and PAES-II of Examples 36 and 37 are injectionmolded and tested in Example 36. The results are given in Table VI.

All of the polyimides, polyamide-imides and poly(aryl sulfones)discussed up to this point are made by conventional solution techniques.The following is an example of a polyimide made in an extruder using apoly(aryl sulfone) as the solvent.

Example 38

A 60/40 blend of PAES-I and PI-VI is made in the following manner. A drymixture of:

    ______________________________________                                        53.85%            BAP                                                         44.70%            BPDA                                                         1.39%            Phthalic Anhydride                                          100.00%                                                                       ______________________________________                                    

is thoroughly homogenized. Forty percent of this mixture is added to 60%of the PAES-I of Example 36 and extruded in a single screw one inchdiameter (L/D=36) Killion extruder. The extruder has seven zones,including the die, and two vents. The equally spaced seven zones fromthe rear to the die of the extruder have the following temperatures:cold, 570° F., 570° F., 670° F., 670° F. and 670° F.

Under the above conditions, the mixture is extruded at about 2pounds/hour chopped into pellets and then reextruded a second time. Thesecond time through the zone temperatures are all raised to 700° F.,otherwise conditions are the same. The extrudate is chopped, diced, andinjection molded at about 700° F. into a 300° F. mold. The resultingASTM test specimens are used to determine the properties given in TableVI.

Example 39

A 60/40 blend of PAES-II and PI-VI is made in the following manner. Adry mixture of:

    ______________________________________                                        53.85%            BAP                                                         44.70%            BPDA                                                         1.39%            phthalic Anhydride                                          100.00%                                                                       ______________________________________                                    

is thoroughly homogenized. Forty percent of this mixture is added to 60%PAES-II of Example 37 and extruded under identical conditions given inExample 38. The resulting pellets are injection molded and tested asshown in Table VI.

Examples 36 through 39 clearly depict the advantages of miscible blendsover immiscible blends. For example, consider heat distortiontemperature (HDT). PAES-I and PAES-II have similar Tgs and heatdistortion temperatures (214° C. for PAES-I and 224° C. for PAES-II).Blending each with PAI-II to make a 50% blend resulted in the increasein HDT depicted in Table VII. Likewise, a blend of each with PI-VI tomake a 40% blend resulted in the increase in HDT also shown in TableVII. Recall that PAES-I is miscible with both PAI-II and PI-VI (SeeTable V, Examples 4 and 26) while PAES-II is immiscible with both (SeeTable V, Examples 15 and 25). Thus, it is seen that miscibility resultedin a substantial increase in HDT while immiscibility resulted in verylittle.

Comparing Examples 36 to 37 and 38 to 39, it is also seen thatmiscibility produced a substantial benefit in toughness. The miscibleblends (Examples 36 and 38) have significantly higher elongations atbreak, tensile impact strengths, and unnotched Izods than theirimmiscible counterparts (Examples 37 and 39) even though these valuesfor the two controls (J and K) are almost identical.

The improvement in environmental stress rupture resistance (chemical) isalso dramatic. Tensile bars of controls J and K and Examples 36 and 37are loaded in flexure to an outer fiber stress of 3000 psi.Methylethylketone (MEK) is applied to the surfaces. MEK is a commoningredient of paint thinners. The times required for the bars to ruptureare given in Table VIII. Note that both controls are rapidly attacked byMEK and that the immiscible blend is not significantly better. Themiscible blend of PAES-I and PAI-II, however, is unaffected by MEK foran extended period of time.

                                      TABLE VI                                    __________________________________________________________________________                                  Example 36                                                                            Example 37                                                                            Example 38                                                                             Example 39                      ASTM    Control J                                                                           Control K                                                                            50% PAES-I                                                                            50% PAES-II                                                                           60% PAES-I                                                                             60% PAES-II            Composition                                                                            Test Method                                                                           PAES I                                                                              PAES II                                                                              50% PAI-II                                                                            50% PAI-II                                                                            40% PI-VI                                                                              40%                    __________________________________________________________________________                                                           PI-VI                  Tensile Strength                                                                       D-638   10,700                                                                              12,000 11,500  12,400  12,600   10,800                 (psi)                                                                         Elongation (%)                                                                         D-638    84   112     41      10      11         8.5                 Tensile Modulus                                                                        D-638   344   398    412     452     423      452                    (ksi)                                                                         Tensile Impact                                                                          D-1822 144   137    111      88      57       19                    (ft-lb/in.sup.2)                                                              Heat Deflection*                                                                       D-648   214   224    224     223     230      225                    Temperature                                                                   @ 264 psi                                                                     (C.)                                                                          Unnotched Izod                                                                         D-256   No Break                                                                            No Break                                                                             No Break                                                                               63      35       11                    @ 1/8"                                                                        (ft-lb/in)                                                                    __________________________________________________________________________     *Samples annealed at 200° C. for 4 hours prior to testing.        

                  TABLE VII                                                       ______________________________________                                        EFFECT OF MISCIBILITY ON HDT                                                             Example                                                                              Example  Example  Example                                              36     37       38       39                                                   (Mis-  (Immis-  (Mis-    (Immis-                                              cible) cible)   cible)   cible)                                               50% PAI-II-                                                                   40% PI-VI-                                                         Example      50%      50%      60%    60%                                     Composition  PAES-I   PAES-II  PAES-I PAES-II                                 ______________________________________                                        Increase in  10       -1       16     1                                       HDT °C. over                                                           PAES Component                                                                ______________________________________                                    

                  TABLE VIII                                                      ______________________________________                                        CHEMICAL RESISTANCE                                                                          Control                                                                Control J                                                                            K        Example 36                                                                              Example 37                                  ______________________________________                                        Composition                                                                             PAES-I   PAES-II  50%     50%                                                                   PAES-I  PAES-II                                                               50%     50% PAI-II                                                            PAI-II                                            MEK at 23° C.                                                                    Rupture  Imme-    No effect                                                                             Immediate                                 and 3000 psi                                                                            after    diate    after   Rupture                                             5 min.   Rupture  24 hrs.                                           ______________________________________                                    

Although the invention has been described in conjunction with specificembodiments, it is evident that many alternatives and variations will beapparent to those skilled in the art in light of the foregoingdescription. Accordingly, the invention is intended to embrace all ofthe alternatives and variations that fall within the spirit and scope ofthe appended claims.

We claim:
 1. A miscible blend of a poly(aryl sulfone) and a polyimidehaving a single Tg when determined by the modulus-resilience method,said blend comprising:(a) a poly(aryl sulfone) containing the followingunit: ##STR30## (b) a polyimide containing the following unit: ##STR31##wherein X₄, X₅ and X₆ are independently --O--, --CO--, --SO₂, --NHCO,--C(CH₃)₂ --or a direct bond with the proviso that at least one of X₄,X₅ and X₆ isopropylidene, and U, V and W are independently 0 or 1, withthe proviso that at least one of U or V is
 1. 2. The miscible blendaccording to claim 1, wherein the poly(aryl sulfone) comprises polymersor copolymers having the following recurring unit: ##STR32##
 3. Themiscible blend according to claim 1, wherein the poly(aryl sulfone)contains the following recurring unit: ##STR33##
 4. The miscible blendaccording to claim 1, wherein the poly(aryl sulfone) contains thefollowing recurring unit: ##STR34##
 5. The miscible blend according toclaim 1, wherein the polyimide contains the following recurring unit:##STR35## wherein X'=--O--.